Since your gun doesn't have choke tubes what is it choked?
Not a lot of info to go on, but you might try the 3" Federal Flitecontrols. The Flitecontrol wad might extend your pattern a bit farther since I doubt your barrel is choked tighter than "full".
If you decided to go with the Heavyweights, the #7's (if you can find them) work very well.